Investigation of copper metallization induced failure of diode structures with and without a barrier layer

Different metallization systems Cu/Si, Cu/Ti/Si, Cu/W/Si and Cu/TiN (N/Ti ratio <1 and approximate to 1)/Si were prepared on n(+)p-diodes. After sequential annealing in H-2-atmosphere these structures were investigated by electrical and analytical methods. For a metallization without barrier layer the electrical breakdown is caused by the formation of Cu3Si. Randomly distributed reaction spots are visible on the silicon surface. For Ti and W the electrical failure occurs after annealing at 450 degrees C in H-2-atmosphere. The breakdown of diodes with TIN is first found for barrier layers with a N/Ti-ratio <1 after annealing at 650 degrees C. Stoichiometric TiN-barriers are stable after annealing at 650 degrees C. The electrical breakdown can be assigned to failure mechanisms determined by the barrier film properties.